fix(test): add missing media dedup state fields to mock contexts

Pre-existing test mocks lacked pendingMessagingMediaUrls and
messagingToolSentMediaUrls fields added by the media dedup feature,
causing runtime errors in handleToolExecutionEnd.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/agents/pi-embedded-subscribe.handlers.tools.media.test.ts

@@ -23,8 +23,10 @@ function createMockContext(overrides?: {
       toolSummaryById: new Set(),
       pendingMessagingTexts: new Map(),
       pendingMessagingTargets: new Map(),
+      pendingMessagingMediaUrls: new Map(),
       messagingToolSentTexts: [],
       messagingToolSentTextsNormalized: [],
+      messagingToolSentMediaUrls: [],
       messagingToolSentTargets: [],
     },
     log: { debug: vi.fn(), warn: vi.fn() },